Firefighters utilize pumper trucks to increase the pressure of water supplied by sources such as fire hydrants and to direct the pressurized water through fire hoses. Sources of water for pumper trucks can also include internal and external tanks as well as natural bodies of water. In certain circumstances, foam or other extinguishants may be used in combination with or in lieu of water.
A pumper truck includes a control panel controlling valves fluidly connected upstream and downstream from a pump used to pressurize the fluid extinguishant. These valves, which are utilized to control the flow of extinguishant to and from the pump, are controlled at the control panel by either purely mechanical or electrical valve actuators. A variety of valves useable with either electrical or mechanical actuators are disclosed in U.S. Pat. No. 7,516,941, the entire disclosure of which is hereby explicitly incorporated by reference herein.
Purely mechanical valve actuators can take a number of forms, but are defined by the transfer of force supplied by a user (a firefighter) to the valve body either directly or via a mechanism such as a mechanical linkage or a gear set. Mechanical actuators therefore rely on user supplied force to actuate the valve bodies. Examples of mechanical actuators include levers that are connected to a trunnion extending from a valve body for rotation therewith, and handwheels that can be rotated by a user to drive a worm gear meshed with a gear sector secured to the trunnion extending from the valve body. In mechanical embodiments utilizing a lever secured to the trunnion, a mechanical linkage may be interposed between the user interface (e.g., a T-handle) and the lever. The force supplied by the user may be amplified by the mechanism employed to transfer the user input force to the valve body, but mechanical valve actuators remain very difficult to actuate in certain circumstances, such as when fluid is flowing through the conduit in which the valve body is positioned.
Contrary to mechanical actuators in which the actuation force is supplied by the user, electrical valve actuators utilize motive force supplied by a motor which is triggered to actuate the valve by a signal stemming from a user input such as a push button. With electrical valve actuators, the force utilized to move the valve body between the open and closed positions is supplied solely by the motor, with the user not supplying any of the force utilized to move the valve body. The electric motor may be used to turn a shaft bearing a worm gear that is meshed with a gear sector secured to the trunnion extending from the valve body.
While electrical actuators provide a number of advantages, including ease of use and easily repeatable re-positing; firefighters tend to prefer the tactile feedback provided by a mechanical actuator. The push buttons used to activate electrical actuators can also be quite difficult to actuate with a hand encumbered by the bulky gloves worn by firefighters for protection. Electrical actuators, such and the UBEC and EXM controllers available from Elkhart Brass Company, Inc. of Elkhart, Ind., utilize a number of push buttons to trigger signals to a motor arranged for driving the valve body. These buttons do not provide the tactile feedback of the purely mechanical actuators and can be difficult to operate with a gloved hand.